1. Field of the Invention
The present invention relates to a motor with brush, more particularly to terminal structures for connecting brushes of the motor to an external circuit.
2. Description of Related Art
A typical motor with brush includes a stator, a rotor having a rotary shaft and a brush section that is in sliding contact with a commutator that is retained at the rotary shaft of the rotor. Driving coils of the motor are energized through the brush section and the commutator. As a result, energization on the driving coils is switched according to rotational positions of the rotor, such that electromagnetic attraction and repelling forces between the rotor and the stator are continuously generated in one direction to continuously rotate the rotor. The brush is retained on the side of the stator in a manner to have a predetermined relative positional relation with the commutator, and is equipped with a terminal that allows the brush to be connected to an external connection member for supplying an external electrical power to the motor. The brush section that includes the terminal may have a variety of designs.
A conventional structure of a brush section of a motor with brush is shown in FIGS. 9(a) and 9(b). In FIG. 9(a), a terminal for a brush (hereafter referred to as a xe2x80x9cbrush terminalxe2x80x9d) 11 is bonded to a brush section 19 in a unitary fashion. The brush terminal 11 include a leg section 13 and bendable claw sections 18 on both sides of a base section of the leg section 13. The brush terminal 11 has a base section with retainer claw sections 16, which is press fitted in an insertion aperture of an insulation resin holder 20 such that the retainer claw sections cut into wall surfaces of the insertion aperture of the holder 20. Then, as shown in FIG. 9(b), the claw sections 18 are bent such that the holder 20 is held between the claw sections 18 and a stepped section 12 of the brush terminal 11, to thereby position and fix the brush terminal 11 to the brush section 19.
Another conventional structure of a brush section of a motor with brush is shown in FIGS. 10(a)-10(d). In FIG. 10(a), a brush terminal 22 is bonded to a brush section 21 in a unitary fashion. The brush terminal 22 includes a first power supply terminal section 23 that extends from the brush section 21 and a second power supply terminal section 24. The brush terminal 22 is affixed to an insulation member such as a resin holder in a manner that the first power supply terminal section 23 and the second power supply terminal section 24 protrude externally from a motor case 25, as shown in FIG. 10(b).
In an example shown in FIG. 10(b), the motor is mounted on a substrate 26, and the second power supply terminal section 24 is fitted in a hole provided in the substrate 26 and soldered to a circuit pattern on the substrate 26. In this example, since the first power supply terminal section 23 is not required, the first power supply terminal section 23 can be removed, as shown in FIG. 10(c).
An example shown in FIG. 10(d) uses the first power supply terminal section 23. In this example, an outer circumference of the motor together with the first power supply terminal section 23 is fitted in a hole formed in the substrate 26, and the first power supply terminal section 23 is soldered to a circuit pattern on the substrate 26. In this case, the second power supply terminal section 24 is removed.
A lead wire for power supply is soldered to the brush terminal, or the brush terminal is soldered to a circuit pattern on the substrate. At the time of the soldering work, the resin holder may melt and deform, such that the position of the brush may be changed. If the position of the brush is changed, the timing to switch power to the driving coils may be deviated, which causes a fatal defect for the motor with brush. In view of this problem, the claw sections of the brush are bent to hold the resin holder by the claw sections and the stopped section of the brush terminal as indicated in FIG. 9. However, the structure shown in FIG. 9 as described above is not perfect as a countermeasure against the heat problem at the time of soldering work, and the shape of the terminal become complicated.
Also, in any of the conventional terminal structures described above, the disposed position of the brush determines the position of the terminal. If the locations of the brushes in a pair are separated from each other, the locations of the terminals in a pair are separated from each other accordingly. For example, in the case of a motor having four poles of magnets and six poles of cores, brushes in pairs are oriented in mutually orthogonal directions, and accordingly the positions of terminals in pairs are separated 90 degrees from one another around the rotational center of the motor. FIGS. 8(a) and 8(b) show a comparison between the above motor structure with four poles of magnets and six poles of cores and an ordinal motor structure with two poles of magnets and three poles of cores. FIG. 8(a) indicates the motor structure with two poles of magnets and three poles of cores, in which brush sections 30 in a pair are generally in parallel with each other, and terminals 31 in a pair are located relatively close to each other. FIG. 8(b) indicates the motor structure with four poles of magnets and six poles of cores. Since brush sections 30 in a pair extend in directions at generally 90 degrees to each other, terminals 31 in a pair are widely separated from each other. For this reason, external connection members such as lead wires are disposed separated from each other, which becomes to be an obstacle to automated and more efficient wiring works. Furthermore, the conventional examples indicated in FIGS. 9 and 10 have a disadvantage in that the shape of the terminals becomes complicated when the positions of the terminals in pairs are converged in order to automate and improve efficiency of wiring works.
The present invention has been made to solve the problems of the conventional technology, and therefore the present invention provides a motor with brush that can prevent the positions of brush terminals and brush sections from being changed by heat caused by soldering when external connection members such as terminals and lead wires are soldered to the brush terminals.
The present invention also provides a motor with brush that can increase the fixing strength of a brush terminal that is boned to a brush section in a unitary fashion.
The present invention further provides a motor with brush in which terminals of the motor to be connected to external connection members can be readily arranged in any optional positions without being restricted by mutual positions of two brush sections in a pair, and terminals to be connected to external connection members can be lead out to an external circumferential side or a rear surface side of the motor depending on the requirements.
In accordance with an embodiment or the present invention, a motor with brush is equipped with a brush section and a brush terminal that is connected to the brush section in a unitary fashion, wherein the brush terminal may include a brush connecting section having a plane that is connected to the brush section, and a bent section that is bent in a direction orthogonal to an axial direction of a rotary shaft of the motor. The bent section restricts the positions of the brush terminal and the brush section.
By forming the bent section at the brush terminal in a manner described above, the bent section function as a stopper section to prevent the position of brush section from moving in the axial direction, and prevents the positions of the brush terminal and the brush section from moving by heat caused by soldering when external connection members are soldered to the brush terminal.
In the above embodiment, the external connection member may preferably be connected to the bent section of the brush terminal, which simplifies the structure of the brush terminal.
In the above embodiment, the external connection members define external connection terminals that protrude from an outer circumferential surface of the motor may preferably have plane sections formed inside the outer circumferential surface of the motor in a direction orthogonal to an axial direction of a rotary shaft. By forming the external connection terminals to have plane sections inside the outer circumferential surface of the motor in a direction orthogonal to an axial direction of a rotary shaft, the bent sections of the brush terminals can be readily, electrically connected to the plane sections of the external connection terminals.
Also, in the embodiment described above, the bent sections of the brush terminals may be disposed to overlap the external connection terminals. As a result, the external connection terminals are prevented from being raised when the brush terminals and the external connection terminals are soldered together, and also the fixing strength of the brush terminals can be increased as a result of connecting and fixing the brush terminals to the external connection terminals.
Also, in the embodiment described above, the external connection terminals may be formed from plate-like members that can be mounted on a motor in parallel with a side plate of the motor, wherein each of the external connection terminals may have an extended section that extends in a circumferential direction of the motor to be connected to the brush terminal and a terminal section that extends in a radial direction of the motor. As a result, connecting points of the motor to external connection members can be readily arranged in any optional positions by optionally designing the shape of the respective extended sections, without being restricted by mutual positions of the two brush sections in a pair. Further, the connecting points to external connection members can be formed anywhere on the motor, e.g., on an outer circumferential side or a rear surface side of the motor depending on the requirements.
It is noted that the brush terminal may be press-fitted in an aperture of a brush holder to retain the brush terminal wherein the brush terminal pressed-fitted in the aperture functions to restrict the position of the brush terminal, in combination with the bent section that serves to restrict the position of the brush terminal in the rotary axis direction. As a result, movements of the positions of the brush terminals and brush sections can be more securely prevented.
Other features and advantage of the invention will be apparent from the following detailed description, taken in conjunction with the accompanying drawings that illustrate, by way of example, various features of embodiments of the invention.